There is a battery pack that couples a plurality of unit batteries, taking a cylindrical battery as a unit battery to integrate this plurality of unit batteries in a coupling state using, for example, a heat shrinkable tube. Then, in the battery pack, the unit batteries are often mutually coupled in series to obtain high output voltage. FIG. 1 exemplifies a location and a coupling state of the cylindrical batteries that constitutes the battery pack. FIG. 1 illustrates an example where two cylindrical batteries (10u, 10d) that will be a main body (hereinafter referred to as a battery pack main body) 1 of the battery pack are coaxially coupled in series. In the following, a direction of an axis 100 of the cylindrical batteries (10u, 10d) is an up and down direction. Up and down respective directions are specified as convex positive electrode terminals 11 are formed on upper end surfaces of these cylindrical batteries (10u, 10d). In the battery pack main body 1 illustrated in FIG. 1, the positive electrode terminal 11 of the cylindrical battery 10d is coupled to a negative electrode terminal 12 of the cylindrical battery 10u via a tab 20 formed of a metal plate. The tab 20 is mounted on the positive electrode terminal 11 of the cylindrical battery 10d and the negative electrode terminal 12 of the cylindrical battery 10u by welding (for example, spot welding). Thus, the cylindrical batteries (10u, 10d) are coupled with smaller electrical resistance. The welding also ensures a mounting strength between the cylindrical batteries (10u, 10d) and the tab 20 to also prevent electrical contact from being unstable, for example, by vibration. Then, the battery pack is configured to fix two cylindrical batteries (the two cylindrical batteries 10u, 10d in the example illustrated in FIG. 1) coupled in series in such coaxially disposed state by the heat shrinkable tube to maintain an outer shape, and to mount, for example, a terminal plate and a lead wire for supplying electric power to an external device on the positive electrode terminal 11 of the cylindrical battery 10u and the negative electrode terminal 12 of the cylindrical battery 10d that are coaxially disposed.
FIGS. 2A to 2C are views illustrating an exemplary assembling procedure of the battery pack main body 1 illustrated in FIG. 1. First, as illustrated in FIG. 2A, a strip-shaped metal plate 120 is bridged across the positive electrode terminal 11 of one cylindrical battery 10d and the negative electrode terminal 12 of another cylindrical battery 10u of the two cylindrical batteries (10u, 10d) that will be coupled in series. In this state, the metal plate 120 is mounted on the terminals (12, 11) of the respective cylindrical batteries (10u, 10d) by a method such as spot welding. Next, as illustrated in FIG. 2B, the metal plate 120 is folded to be the tab 20 formed by folding the metal plate 120 in two as illustrated in FIG. 2C, thus coaxially disposing the two cylindrical batteries (10u, 10d). Following Patent documents 1 and 2 disclose a technique that couples a plurality of cylindrical batteries in series by welding a metallic dish component to the cylindrical batteries without a tab.